Virtual reality (VR) and augmented reality (AR) visualization systems are starting to enter the mainstream consumer marketplace, such as in the form of head-mounted display (HMD) devices (“AR-HMD devices”). AR-HMD devices are a promising application of VR and AR technologies.
AR-HMD devices can be embodied in a wearable headset that is arranged to display an image within a short distance from a human eye. Some AR-HMD devices are provided with a frame which has a central portion fitting over a user's (wearer's) nose bridge and left and right support extensions which fit over a user's ears. Optical components are arranged in the frame so as to display an image within a few centimeters of the user's eyes. The image can be a computer-generated image on a display, such as a micro display. The optical components are arranged to transport light of the desired image which is generated on the display to the user's eye to make the image visible to the user. The display on which the image is generated can form part of a light engine, such that the image itself generates collimated light beams which can be guided by the optical component to provide an image visible to the user.
Different kinds of optical components have been used to convey the image from the display to the human eye. These can include lenses, mirrors, optical waveguides, holograms and diffraction gratings, for example. In some display systems, the optical components are fabricated using optics that allow the user to see the image, but not the “real world”. Other types of display systems provide view-through optics, so that the generated image which is displayed to the user is overlaid onto a real-world view (i.e., AR).
Waveguide-based display systems typically transport light from a light engine to the eye via a TIR (Total Internal Reflection) mechanism in a waveguide (light guide). Such systems can incorporate diffraction gratings, which cause effective beam expansion so as to output expanded versions of the beams provided by the light engine. This means the image is visible over a wider area when looking at the waveguide's output than when looking at the light engine directly. Provided the eye is within an area such that it can receive some light from substantially all of the expanded beams, the whole image will be visible to the user. Such an area is referred to as an eye box.
Components of AR-HMD devices may require very precise positioning and alignment within the devices in order to function properly. Even minor mechanical or thermal stresses applied to these components (e.g., waveguides) can potentially affect the positioning or alignment of such components and thereby adversely affect functionality of the devices. Additionally, these components may be vulnerable to damage due to being dropped or other impacts, normal handling, or environmental factors.
It is with respect to these considerations and others that the disclosure made herein is presented.